1. Field
This disclosure relates to a multifunction enclosure to protect fuel tanks mounted behind a tractor cab.
2. General Background
Pressurized cylinders are useful; for storing and transporting fuels such as hydrogen, natural gas (CNG) and propane. Storage of gaseous fuel cylinders/tanks in a tractor or trailer must meet crash safety requirements. Tractor Trailers have many different weight ratings which may affect their usage and the cost of usage. Gross Vehicle Weight (GVW). This is the total weight of the loaded vehicle. This includes the vehicle itself and the cargo that is loaded on the vehicle. Gross Combination Weight (GCW). This is specified by the manufacturer as the maximum loaded weight of a truck/tractor plus the trailer or semi-trailer designed for use with the truck/tractor. Gross Vehicle Weight Rating (GVWR). This is the rating that is calculated by the manufacturer as the amount of weight that the vehicle will be when the vehicle itself is weighed filled with fuel and loaded according to the manufacturer's specification.
Gross Combination Weight Rating (GCWR). This is the maximum allowable combined mass of a towing road vehicle, passengers and cargo in the tow vehicle, plus the mass of the trailer and cargo in the trailer. This rating is set by the manufacturer.
Any vehicle operating interstate with a GVW or GCW or registered weight of 26,000 lbs. or more, or having three axles at any weight, is subject to the International Registration Plan (IRP) for apportioned registration and the International Fuel Tax Agreement (IFTA) for payment of fuel use taxes. These base state agreements do not use the vehicle weight rating when determining compliance.
Highway Weight. This is the legal weight related to highway size and weight limits. When operating on the interstate system, the maximum permissible weight is 20,000 lbs. on a single axle, 34,000 lbs. on a tandem axle, and 80,000 lbs. max gross weight. The “Bridge Formula” allows motor vehicles to be loaded to the maximum weight only if each group of axles on the vehicle and their spacing also satisfy the requirements of the formula. States must use these limits for their designated or national network highways. While the majority of the states use the federal bridge formula for all roads in their state, some do have a separate state formula for other state or county roads.
Weight costs fuel and reduce load carrying capacity. Turbulent airflow around a tractor trailer increases the drag coefficient and reduces mileage. Improving laminar airflow is a design goal in most modern motor vehicle designs. FIG. 1 shows fuel system 5 of gaseous fuel tanks 10 secured to a rack 15. The fuel system 5 is secured behind a tractor cab. Valves 18 on the end of the tank are used to provide an outlet for supplying gaseous fuel. The valves should be protected during transport of the tanks behind a tractor.